docs: def get_tags(doc):
      '''
      Get tags from a DOM tree
  
      :param doc: lxml parsed object
      :return:
      '''
      tags = list()
  
      for el in doc.getroot().iter():
          if isinstance(el, lxml.html.HtmlElement):
              tags.append(el.tag)
          elif isinstance(el, lxml.html.HtmlComment):
              tags.append('comment')
          else:
              raise ValueError('Don\'t know what to do with element: {}'.format(el))
  
      return tags